This invention relates generally to sensing and protective components used in conjunction with an automotive battery-powered system, and more particularly to a way to provide advance warning of when a vehicular disabling event related to such fuse opening is about to occur.
Batteries using lithium-ion (Li-ion) or other chemistries are being used in transportation applications as a way to supplement, in the case of hybrid electric vehicles (HEVs), or supplant, in the case of purely electric vehicles (EVs), conventional internal combustion engines (ICEs). The ability to passively store energy from stationary and portable sources, as well as from recaptured kinetic energy provided by the vehicle and its components, makes such batteries ideal to serve as part of a propulsion system for cars, trucks, buses, motorcycles and related vehicular platforms. In one form suitable for automotive applications, individual battery cells are combined into larger assemblies such that the current or voltage is increased to generate the desired power output. In the present context, larger module and pack assemblies are made up of one or more cells joined in series, parallel or both, and include additional structure to ensure proper installation into the vehicle. Although the term “battery pack” is used herein to discuss a substantially complete battery assembly for use in propulsive power applications, it will be understood by those skilled in the art that related terms—such as “battery unit” or the like—may also be used to describe such an assembly, and that either term may be used interchangeably without a loss in such understanding.
It is desirable as part of the electrical connectivity between the various individual cells within the battery pack, as well as between the battery pack and the electrical loads discussed above, to include sensing circuitry (such as voltage-sensing or current-sensing variants) to allow for monitoring and the related detection of abnormal voltage conditions within the pack and various battery cells. Moreover, it is desirable to have voltage isolation circuitry responsive to such sensing circuitry to allow for shutdown or related corrective measures to be taken in the event an anomalous condition arises during the operation of the vehicle; one form of voltage isolation circuitry that is used by the Assignee of the present invention is known as a manual service disconnect (MSD) as described in U.S. Pat. No. 8,574,004—the entirety of which is incorporated by reference herein—that permits a simple disconnect for service or emergency response personnel to reduce their exposure to the full voltage of the battery pack. These and other circuits are connected to the battery packs and other electronic components (such as one or more automobile electronic control units (ECU) that in turn embody hardware and software features to define one or more computers, controllers or the like) to provide integration of the vehicle's electrical power and control systems.
One significant part of the electrical connectivity discussed above is in the form of fail-safe components, such as circuit breakers or fuses that are designed to cause an open circuit when a particular electrical parameter (such as current) exceeds a predetermined threshold. In a conventional form, the fuse is an “off-the-shelf” component that is subject to limitations in its operational consistency due to variations in manufacturing, material quality or the like. In fact, fuse part-to-part variation has been identified as being as high as 60%, and that much of this is due to variations in fatigue life arising from inconsistencies in punch tool sharpness and material properties, as well as fatigue damage that may have accumulated before final assembly. The present inventors have determined that fatigue failure from these and other causes leads to shortened fuse service life. More particularly, because conventional sensing circuits cooperate with the ECU through an algorithm or related program that is based on a worst-of-the-worst (WOW) part failure assumption, these variations in fuse-opening events (also referred to herein as fusing events) tend to cause diagnostic codes (also referred to as diagnostic trouble codes (DTCs)) that are integrated into the ECU's on-board diagnostics (OBD) system to err on the side of extreme caution. This overly conservative assumption of when the fuse will open leads to inordinate amounts of vehicle shutdown and concomitant operator/passenger displeasure, as well as increases in false maintenance reporting and procedures. The present inventors have additionally determined that these variations in fusing events are particularly problematic when differences in driving habits are taken into consideration, as vehicle operators with more aggressive driving habits are more likely to pre-maturely trigger an actual fuse open event than a vehicle operator with more docile driving habits. For example, a conventional DTC may be programmed for the more aggressive driving parameters; because component reliability requirements are often set at extremely high values to take into consideration a WOW fuse, a vast majority of the fuses installed in vehicles in general (and vehicular battery systems in particular) have their useful life limited to that of the WOW fuse.
As such, what is needed is a way to take into consideration variations in the conditions that lead to fuse open events, as well as ways sensing circuits respond to such variations. What is further needed is a way to detect impending fuse openings prior to an actual opening event; this early detection allows the DTC to be activated to alert a user to take a vehicle in for service rather than wait for a fuse open event that may result in a loss of current being delivered from the battery to the vehicle's propulsion system. Additionally, what is needed is such a configuration that achieves this warning with reduced false alerts.